Curcumin, [1,7-bis(4-hydroxyl-3-methoxyphenyl)-1,6-heptadiene-3,5-dione], is the major constituent of the spice turmeric extracted from the root of Curcuma longa Linn. Curcumin is a polyphenol that has powerful antioxidant and inhibits the expression of the enzyme cyclooxygenase 2 (Cox 2) at least in part via interference with activation of the transcription factor NFkB [2, 14]. In vitro, curcumin inhibits the growth of cancer cells with an IC50 value of 20-75 μM [6, 16]. In rodent models, curcumin has been shown to prevent cancer in the colon, skin, stomach, duodenum, soft palate, tongue, sebaceous glands and breast [9, 10, 15]. Therefore, curcumin could be considered a promising efficacious and safe cancer chemopreventive agents [18]. In fact, clinical pilot studies have associated curcumin consumption with regression of pre-malignant lesions of bladder, soft palate stomach, cervix and skin [1, 11].
However, concentrations of curcumin achieved in plasma and target tissues are low, probably due, at least in part, to its extensive metabolism by conjugation (glucuronidation and sulfation) and reduction pathways [4, 5, 7, 8].
Preclinical and clinical pilot studies suggest that In a phase I trial plasma and urine concentrations of curcumin in patients, who had ingested 3600 mg curcumin orally, were 11.1 nmol/L and 1.3 μmol/L, respectively [17]. In another study, peak plasma concentrations 1-2 h after oral dosing, reached 0.41-1.75 μM in patients receiving 4 to 8 g curcumin [1]. It is neither practical nor desirable to increase the oral dose of curcumin above that already investigated.
Therefore, it is highly desirable to find novel curcumin derivatives having improved bioavailability.
Complex compounds of vegetable extracts or of purified components thereof with natural, synthetic or semi-synthetic phospholipids, have been disclosed, e.g., in EP 209 038, EP 275 005, EP 283 713, EP 1 035 859 and EP 1 140 115. Said complexes improve the plasma bioavailability of the extract or purified component, thanks to their lipophilicity. EP 1 140 115 generically mentions ethanol among the various solvents that can be used of the preparation of said complexes, but does not provide preparation examples which make use of ethanol as the solvent. Furthermore, the complexes disclosed are phospholipid complexes of proanthocyanidin A2, which are quite different in the chemical structure with respect to the phospholipids complexes of curcumin of the present invention.